This sounds awful and upsetting for you (particularly the bullying fears). My child is sometimes kleptomaniac and takes other kids stuff - especially toy money! You have just reminded me that I need to follow this up more and find and return items she takes. We don't endorse stealing, we're just a busy busy family. I would explain to the other mum how important this toy is to your daughter and ask her if she could have an extra special look? Other mums have asked me this before - luckily for items my daughter's properly borrowed though :-) Good luck!